Disk drives are widely used in computers and data processing systems for storing information in digital form. Disk drives typically utilize one or more rotating, storage disks and a plurality of data transducers to interact with each storage disk. An E-block having a plurality of spaced apart actuator arms retains the data transducers proximate each storage disk. An actuator motor moves the E-block and the data transducers relative to the storage disks.
The need to rapidly access information has led to disk drives having storage disks which are rotated at ever increasing speeds and an actuator motor which moves the E-block at ever increasing rates. Unfortunately, this typically results in increased heat, noise and power consumption of the disk drive.
FIG. 1 illustrates a rear perspective view of a portion of a prior art, rotary, voice coil actuator motor 100. In this embodiment, a flat, trapezoidal shaped coil 102 is positioned between two permanent magnets 104 and two flux return plates 106. The coil 102 is secured to the E-block (not shown). Current passing through the coil 102 causes the coil 102 to move relative to the permanent magnets 104 to move the E-block.
One factor which effects efficiency of the actuator motor 100 is the strength of the magnets 104. In the prior art actuator motor 100 illustrated in FIG. 1, the magnets 104 include magnetization lines 108 (illustrated as arrows) which are oriented substantially perpendicular to the coil 102. Unfortunately, with this design, the strength of these magnets 104 vary approximately 14-20 percent across the stroke of the coil 102. More specifically, the strength of the magnets 104 is high, near the center and drops near the sides of the magnets 104. This non-linearity causes difficulty in precisely moving the coil 102. Inaccurate positioning of the coil 102 leads to data transfer errors between the data transducers and the storage disks.
One attempt to solve this problem involves flattening the magnet strength at the center of the magnets 104 so that the strength of the magnets 104 is approximately linear. This can be done by reducing the flux in the flux return plates 106 by thickening the flux return plates 106 and thinning the magnets 104 near the center. Unfortunately, this reduces the average strength of the magnets 104 and increases data retrieval times of the disk drive.
In light of the above, it is an object of the present invention to provide a efficient magnet for devices such as actuator motors for disk drives. It is another object to provide a permanent magnet for a disk drive which is relatively easy to manufacture. Yet another object is to provide a permanent magnet which significantly improves the performance of the actuator motor and provides substantially linear movement of the actuator motor.